Hoist control mechanism



Filed July 31, 1941 N mm mN o T R L B EZY LL 9 (AAA ATTORNEY I PatentedJune 27, 1944 ,UNITED STATES PATENT OFFICE HOIST CONTROL MECHANISMBurton S. Aikman, Wilkinsburg, Pa., assignor to Q The Westinghouse AirBrake Company, Wilmerding, Pa.,a corp'orationoi Pennsylvania ApplicationJuly 31, 1941', Serial No. 404,859

8 Claims, (c1. 60-51) This invention relates to hoist .or elevatorcontrol systems and more particularly to the hydropneumatic type inwhich a liquid such as oil is displaced by compressed air for actuatinga pis ton orthe like to elevate a body.-

One object of the invention is the provision of an improved system ofthis type.

Another object of the invention is the provision of a system ofthistype'in which the liquid pressure actuatedhoisting piston or element cannot drop in case of failure of the supply of'compressed air on thehoisting liquid as during or after the completion of a hoistingoperation. 7 Another-object of the invention'is the provision of animproved hoist control system of the hydropneumatic typ embodying meansfor reclaiming the compressed air used toefiect a hoisting operation soas to accelerate the restoration of the compressed air suppl inpreparation for a subsequent hoisting operation and to also minimize theamountof power consumed in maintaining the "required amount ofcompressed air for operating the system: Q I 1 Other objects andadvantages will be appar ent from the followin more detailed descriptionof the invention. p I

l v Description In the accompanying drawing the single figure -is adiagrammatic view, mainly'in section, of the improved hoist orelevatorcontrol system.

In the drawing the reference numeral 1 indicates a compressed airstorage reservoir which, when the system is-in use, is adapted to'bemaintainedcha-rged, with air at apressure between chosen limits suchas-from one hundred and fiftyfive to one hundred and seventy-five poundsper square inch,-and'from' which compressed air is adapted 1 to be drawnor used for controlling hoisting or elevating operations, in a manner tobe described. 1i The reference numeral '2 indicates an aircompressorwhich for the purpose of illustration is preferably of thecompound type comprising a low pressure piston 3 and a high pressurepiston 4.1 These pistons are connected for operation to a crankshaft 5whichissuitably supportedin endbearing's 6, only one of 'which isshownrThe crankshafti extends through the one endbears ing 6 and on fitsouterv endtis provided with-a pulley? which'by means of. abelt 8 isoperatively connected to a driveshaft 9 ofzan relectric'xnotor Ill.Outboard of. the crankshaft bearing 6 the compressor casing carries an.oilseal II which contacts theperiphery of the crank shaft extend-- ingtherethrough. This seal isoi the pressure. type adapted to preventleakage of lubricating oilfrom the crank case I2 along the crank shaft 5when the pressure in the crank caseis above that of the atmosphere. I I

In operation the low pressure piston 3 is adapted to drawair from anintake pipe 13 and to compress same, into one end of an intercooler l4,the opposite end of which is connected to the intake for the highpressure piston 4. I The high pressure piston is then adapted tocompress the air. taken from. the intercooler and to discharge samethrough a discharge pipe l5 into reservoir I. In order to substantiallyequalize the forces on the two pistons while operating, the displacementof the low pressure piston. 3 is preferably such as to provide apressure in the intercooler l4 of for instance substantially fortypounds per square inch when the intakepipe I3 is open to the atmosphereproviding for the charging of the low pressure cylinder at substantiallyatmospheric pressure. The high pressure piston is adapted to increasethe pressure from that in the intercooler to the degreedesired in thereservoir I, such as from one hundred and'fiftyefive to one hundred andseventy-five pounds per square inch above mentioned. I I l e Theelectric motorlll is adapted to be controlled by an electric governor 20of any desired type which will respond to the pressure in the reservoirI. This governor may be adjusted to open the circuit through the motor10 for stopping'the compressori2 when the pressure in the reservoir I isincreased to the desired degree such as one hundred and seventy-fivepounds above mentioned, and to close said circuit when the pressure inthe reservoir becomes reduced-to a certain lower degree such as onehundred and fifty-five pounds,'so as to cause the motor lll to operatethe compressor 2 forrrestoring the pressure in said reservoir.

The. pressure. governor is preferably associated with a cutout device 2|which under a certain condition to be later described is adapted to render said governor non-responsive to the pressure of the compressed'airin the reservoir I;

The'cutout device 2| comprises a casing-having'a passage 22 eonnectingthe governor to a chamber 23 which normally is "open past a valve 24 toa passage 25 in constant communication with the reservoir I. Withthevalve 24 open as shown, the governor 20 is'therefore'connected to thereservoir I so' as to operatein thenormal manner in response to pressurevariations in said reservoir.

The valve 24 is provided on one end of a stem 26 on the opposite end ofwhich is a valve 21 arranged to control communication between chamber 23and a chamber 28 which is open to the atmosphere through a passage 29. Acontrol spring 39 in chamber 23 acts on an annular collar 3| provided onthe stem 26 for urging the valve 21 closed and for opening the valve 24.A pin 32 projects from the valve 21 i'ntc chamber 28 in axial alignmentwith a plunger 33. The plunger 33 has on its outer end a, follower 34conis clamped around its edge in the casing. At the opposite side of thediaphragm is a pressure chamber 36 which is connectedto the compressorintake pipe l3 and which under a. condition to be later described isadapted to be charged with fluid under pressure. A chosen relativel -lowpressure, in chamber 36, such as two pounds above atmospheric pressure,is adapted to overcome control spring 36 and deflect diaphragm 35 in thedirection of the left-hand for thereby unseating the valve 21 and forseating the valve 24. When this condition occurs, control passage 22 forthe governor 26 will be opened to the atmosphere through chamber 23 pastthe valve 21- and thence through chamber 28 and port 29 for therebyreducing the control pressure on the governor to a degree s'uchas tocause said governor to operate to close the electric circuit through themotor [0. 1

The reference numeral 49-indicates an oil reservoir containing a bodyof'oil. Mounted on the top of the reservoir 46 is a manual control valvedevice 4| which comprises a; vertically extending control handle 42pivoted at its lower end on a shaft 43. At one side-of the handle 42 isa stand pipe 44 extending through the interior of the reservoir 49 tonear the bottom thereof.

46 is a liquid supply pipe 45adaptedto be connected to the elevatingpiston or plunger (not shown). of the mechanism for conveying liquidunder ressure thereto to effect a hoisting oper-. ation. The device 4|contains a check valve 46 so arranged as to provide .for. flow of liquidin the direction from pipe 44 topipe 45 but to.

automatically prevent flowin the i'opposite direction. A spring 41actingon; check valve 46 is provided for urging same to itsclosediposition shown.-

Apin 48 projects from the end of checkvalve 4610pposite that engaged .byspring 41.. This pin is aligned with a longitudinally movable plunger 49:which isdisposed in Ea suitable bore in the device and has an 'oiltight .fit with the side wall thereof. The outer end of plunger 49 isaligned for movement by. an intermediate portion of a lever 59 which. is.fulcrumed at one end on a pin Ihe opposite end of lever 56 is arrangedto be engaged by one side of handle 42 upon rocking said handle in aclockwise dimotion from the normal position shown to thereby actuatesaid lever' and plunger 49 to unseat the check valve 46. With'the handle42 in its normal position as shown, and also counterclockwise movementof saidhandle fromsaid normal position, the valve 461s adapted to bemaintained seated by spring 41. Y

Above the body of "oil in reservoir '46 is a:chamber 55 to'whichcompressed; air is adapted to be supplied from the reservoir I fordisplacing oil from said reservoir into .pipe .45 to efiect a hoistingoperation and from which compressed air is adapted to be released topermit oil to be Connected to the device- 41 outside of thereservoirtacting one side of a flexible diaphragm which ""air.

released from the pipe for lowering the hoisting element. The supply ofcompressed air to and its release from chamber is adapted to becontrolled by a valve mechanism 56 which forms a part of the manualcontrol valve means 4| but which is located on the side of handle 42opposite the check valve 46.

I The valve mechanism 56 comprises a casing having a chember 51 which isconnected by pipe 58 to the compressed air'reservoir l and thus in useis constantly supplied with compressed In the casing a valve 59 isarranged to control communication between chamber 51 and N a chamber 60which is open to chamber 55 above the oil in reservoir 46. The valve 59is connect- "ed' to a' piston 6| which is subject on one face 'to thepressure of compressed air in chamber 51. 1 At the opposite side ofpiston 6| is a chamber 62 containing a bias spring 63 acting on thepiston for urging the valve 59 to its closed position.v Above the piston6| is a chamber 65 which is in constant communication with chamber 62through a passage 66. A valve 61 contained in the chamber 65 has afluted stem extending through ;a suitable bore in the casing inalignment with the left-hand side of handle 42. Projecting from theopposite side of valve 61 is a pin having on its end a tapered valve 69adapted to cooperate with an aligned seat in the casing. A bias spring19 in chamber 65 acts on the valve 61 for seating same and for unseatingthe valve 69. This condition of these valves is adapted to be maintainedwith the handle 42 in the vertical position shown or upon movementv fromthis position in a clockwise direction. Movement of the handle 42 fromits vertical position in a counterclockwise direction is however adaptedto unseat the valve 61 and seat the valve 69.

The valve 59 is provided for supplying compressed air from the reservoirI to chamber 55 in the oil reservoir 49 and for cutting off such supply. Coaxially aligned with this valve is an oppositely seating valve 15which is provided for controlling the release of compressed air fromchamber 55. The valve 15 is contained in chamber 16 and has a flutedstem 11 which is slidably mounted in a bore connecting said chamber tothe chamber 60. The two valves 59 and 15 are connected together formovement in unlson by a pin 18 connecting the 'stems'of the two valves.

The reference numeral 63 indicates a pressure reducing valve devicewhichhas a chamber 82 to which the inlet pipe 13 of the compressor isconnected. An air cleaner or strainer 66 is connected to the pressurereducing valve device 83 to provide for flow'of air from the atmosphereto the chamber "82 and thenv through the inlet pipe l3,to the aircompressor '2 during its normal operation. This flow of air through thestrainer device to 'chamber'62 occurs :through a chammr 84 containing adisk type-checkvalve 85 adapted to open under such flow but .to closecommunication from chamber '82 to the. atmos phere through the "air.strainer '80 atother itimes.

Chamber 16 in the supply and release valve mechanism 56 is connected-.;by .a pipe '81 to a chamber -88 in thelre'duc'ing valve device '83..A valve 89 is contained in the'chamber. 88 and has a fluted stem "90extending througha bore connecting'said chamber to the chamber 62. A pin9-! :slidably'mounted in a suitable bore :15 connected at one end to thelower :end ot'the valve stem 90 and projects into a chamber. 92 wherein-A -plunge r 95; engagesthe oppositeface ot-the diaphragm. 94 and. isacted upon by a spring 96 which urges the diaphragm in the direction forunseating the valve 89.; The chamber 921s connected to c mber, b a a ewhi chamber 98 containing spring 96-is inconstantcommunication with theatmosphere through a breather port 99. The pressureotspring 99 on thediaphragm 94 is such; as to require a chosen degree of 'fluid pressurein chamber :92, such for example tas forty pounds per square inch, fordeflecting said diaphragm-againstthe spring to thereby permit seating ofthevalve 89; When any lesser degree of' fluid pressure is effective inchamber 92 and thereby in chamber. .82- the spring 99is adapted-tounseat'the-valve 89. l

Operation Y v M Letit be assumed thatlthe reservoir 40; containsan-adequate amount of oil for, controlling hoisting or elevatingoperations and that oil from the-hoist supply pipe 45;has been releasedtosai'd reservoir, in a manner to-be, hereinafter. de.-- scribed,- to adegree whichprovides for lowering of the hoisting element or pistontoits-normal position. Let it also be assumed that the handle 42 is. inthe vertical positionshown inwhich it will be normally carried and thatthe whole. sys-' tem including the air supply reservoir I is void ofcompressed air. Let it further beassumed that the compressor 2 and motor[,0 are-not-operating, due for instance to a line switchlflflin thecircuit of saidmotor being open.

1 To condition the system for operation, switch H .is closedand sincethe pressure in reservoir l is-belowthe cutting-out point of thepressure governor 20, said. governor will close the circuit to the motorl0 andcause'the compressor 2 to operate to draw air from theinlet pipel3 and to compress same into the storagereservoir l. Underthis conditionthe drawing of air from pipe 13 willcreate asufiicient. reduction inpressure in chamber 82 in the pressure'reducing valve device 83to'provide foratmosphericpres sure acting through the strainer device 80on the lower face of the check valve 85 to lift said checkvalvewhereupon thecompressor 2 will draw'air directly from theatmosphere for compressing into the reservoir I. Thecheck valve 85 ispreferably a relatively light weight disk so as" to offer substantiallyno-interference with the-nee flow of air from the atmosphere to thecompressor, as just mentioned.-

During'initial charging of the r I phragm chamber 36in the'cut-ofidevice 21' will beat substantially"atmospheric pressureso that springwill be efiective to maintain valve 21 seated and valve 24 unseated,thereby subjecting the electric governor 2'0 to control by thecompressedair suppliedto thereservoir I, f The'compressor 2 will thus'operate topump air into the reservoir l-until the'pressure in said res ervoir isincreased to the cuttingi'out point of the governor 20, which maybeadjusted to operate to open the circuit through motor I0 when thepressure in the reservoir is increased to the one hundred andseventy-five pounds per square inch above mentioned. When this pressureis attained, the motor 10 and therefore the compressor 2 will bestopped.

' As air is compressed'in'to the reservoir I it flows through pipe 58 tochamber 51 in the manual control device 4| and fromsaid chamber past theline reservoir I 'dia- .stantially at atmospheric pressure.

the unseated valve; 69 to chamber 62 at the oppositefaee of thepiston 6hThe pressure of the air acting on opposite races of the piston 6| thusbeing the same permits the bias spring 63 to hold valve 59-seated.Withvalve 59 seated, the valve 15 is unseatedjso that chamber 55 abovethe oil in reservoir 40 will be opened past the valves 15 and, 89 tochamber 82 which at this time is sub- The valve 89 will be unseatedatthis time by spring 96 due tothe fact that substantially atmosphericpressure will be acting in chamber 92 above the flexible diaphragm 94.The system is now in condition for operation. 7 r .Let it now be assumedthat it is desired to effect araising or elevating operation. Toaccomplish this, the operator moves the handle 42 from the normalvertical position shown in a counter-.- clockwise direction to unseatthe valve 61 and seat the valve 69. When the valve i'lv is unseated, thecompressed air in chamber 62 is vented to the atmosphere past said valvealong the fluted stem .68. The pressure of the air in chamber 51 at theopposite side of piston 6| then moves said piston toward the right-handagainst spring 63and such movement unseats the valve 59 and seats thevalve 15. Compressed air supplied from the storage reservoir I tochamber 51 then flows past the valve 59 to chamber 60 and thence tochamber 55 above the oil in reservoir 40. I .The compressed air thussupplied to chamber 55; and acting on the top of the body of oil inreservoir 4D is adapted to force said oil out through the stand pipe 44to the check valve 46 and un-' seat same against the light bias spring41 so as to then'flow to the pipe leading to the hoisting .means foractuating same to eifect an elevat ing: operation. 5

The amount of oil thus displaced intothe hoist pipe 45. will varyaccording to the height to which it is desiredto elevate the body beingraised,

while thedegree of air pressure required 'in chamber 55. for displacingthe liquid will vary in accordance with the amountof oil it is desiredto displace as well as the weight of the body being elevated.:The'pressure required in chamber above the oil in reservoir 40 maytherefore be equal to the equalization with the pressure in the supplyreservoir l orof any lesser degree. If such equalization is desired, thehandle 42 will beheld in its left-hand position until such occurs andwill then be relieved of manual force. However, if alesser degree of airpressure is desired in chamber 55, then the handle 42 will be held inits left-hand position only until such desired pressure is attained andit will then be relieved of manual pressure; Whenever handle 42 is thusreleased, spring H1 will act to -seat the valve 61' and unseat the valve69 and in so doing will return the handle 42 to its normal verticalposition whereupon compressed air will flow from chamber 57 to chamber62and thus equalize on the opposite faces of' the'piston 6|. Spring 63will then operate the piston 6| to seat the valve 59 for closingcommunication between the supply reservoir 1 and the oil reservoir 40.It will thus be-apparent that any desired degree of displace ment of oilfrom the reservoir 40 may be attained and under any desired actuatingpressure of compressedair.

I It will be'noted that as long as there is flow of oil into the hoistsupply pipe 45 such flow will hold. the check valve 46 op'enbut as soonas the flow'ceases, the check valve will be closed by spring 41 toth'ereby'isolate the hoist supply pipe 45 from any. part of the systemin which-there is compressed air. In case of failure of any part of thesystem in which compressed air is efiectiveor in case ofiailure of thesupply-of compressed air for any reason, the check valve 46 willtherefore automaticallyoperate to prevent back flow of hoisting. liquidfrom. the hoist supply pipe 45 to the reservoir 48'. Thus any suchfailure can not result in an undesiredand possibly disastrous dropping.ofthe elevated load. or body.

When compressedair is drawn from the supply reservoir I for displacingoil from reservoir 40, the pressure of the airin the supply reservoirwill become reduced and if this reductionis below the cutting-inadjustment of the electric governor 20, said governor willoperate toclose the circuit through the electric motor I and cause the compressor2 to operate. to recharge said reservoir. The compressor may be thuscaused to operate to recharge the reservoir .while the handle 42 isbeing held in the left-hand or hoisting position and such operation mayor may not terminate before it is desired to lower the body which waselevated. Moreover, if the amount of compressed air taken from thereservoir I is not sulficient to reduce the pressure therein to thatrequired for causing the governor to start the compressor, the reservoirI will not be recharged with handle 42 in the left hand hoistingposition, as will be apparent. Whenever the handle 42 is returned fromits left hand raising. position to its normal vertical position, thevalve 59 is seated as above described so as to close communicationbetween the supply reservoir I and chamber 55, and at the same time thevalve 15 isvunseated so as to connect .the chamber 55 to chamber 16. Thecompressed air previously supplied to chamber 55 for efiecting ahoisting operationwill then flow to chamber '16 and thence through-pipe.8-! to chamber 88 in the reducing valve device 83. Under this-conditionthe check valve 46 will act to bottle-the liquid in pipe so as tomaintain the body previously elevated in its raised position.

When valve 15 is unseated to connect chamber 55 to the. reducing .valvedevice, the valve 89 therein will be unseated by spring 96, due tothevfactthat the pressure in chambers 82 and 92' will at this instant besubstantially equal to that of the atmosphere. The compressed airsupplied from chamber 55 to chamber 88' will therefore flow-past thevalve 8 9 into chamber 82 and thence through the compressor. intake pipeI3. to diaphragm. chamber 85in the governor cut-out device 2I. and tothe intake of'compressor 2. The pressure of the compressed-airthus-obtainedin chamber 82 of the reducing valvedevice 83 will' seat thecheck valve 85 to preventloss thereof through the strainer device 80,and will also equalize through-port 91- into chamber 92 on-the upperface of diaphragm 94 and when increased therein to a. degree sufficientto overcome. the pressure of. spring 98 will deflectsaid diaphragmdownwardly against, said spring. as to permit movement of the valve 89inthedirection of its seat and thus prevent the-pressure obtained inchamber 82 irom increasing above that determined-by spring 96.,

When a relatively lightdegree of pressurasuch as for instance two poundspersquare. inch, is attained, as above described,.ln diaphragmphamber.35.0f 'thegovernor cutoutdevice 2.'I., the diaphragm 3,5 will-bedeflected in the dircc-tlonof the leit-hand-ag'ainst the pressure 'ofspring'lB'U-L This'movementwill s'hiftthe val-veil 'away'from its seatand seat the valve 24, with the resultthat the governor control passage22-wi1l-be opened to the atmosphere through chamber '23, past the valve2-! and thence through chamber 28 and vent port 29.- The controlpressure for the electric governor 20 will-thus be reduced tosubstar'rtially that of the atmosphere and as a result said governorwill operate to close, if not already closed, the circuit through themotor I 0 to thereby cause said motor to operate thecompressor 2 to takeair out of the intake pipe I3 and to compress same through the dischargepipe I5 into thereservoir-I'.

The compressed air thus taken from the intake pipe I3 and chamber '82 inthe reducing valve device 83 will tend to reduce'the' pressure acting inchamber 92 above thediaphragm 84, as a result of which the control sprin96' will unseat the valve 89' to provide such flow of compressed airfrom chamber into chamber 82 as to maintain a substantial equilibriumbetween the pressure of spring 96 acting on one side of the diaphragm 94and that of the compressed air inchamber 92 acting on the opposite sideof the diaphragm. The spring 96 and diaphragm 84 are so related that themaximum pressure obtainable in cha-mber 82 andat the inlet of thecompressor under this condition will not exceed a desired degree such asforty pounds regardless of the pressure acting in chamber 55' of the oilreservoir 40, which subsequent toequalization with the pressure of airin the reservoir I during a hoisting operation may be as great as forinstance one hundred and fifteen pounds.

-There are several important reasons for employing the reducing. valvedevice 83 to limit the pressure obtained inthe inletpipe I 3 and therebyat the inlet to theeompressor 2 to a certain relatively low degree ascompared to that which may exist in chamber 55 of the oil reservoir 40.Certainof these reasons will now be discussed.

It will be noted that the inlet pipe I3 to the compressor is connectedto the. crank case I2 thereof so that whatever pressure is acting insaid pipe will also? be actingv on the low pressure faces of thecompressor pistons 3 and 4 in opposition to-the pressure of the airbeing, compressed and actin on theupper' faces of the pistons duringoperation of the compressor. The object of this is to minimize the loadson the various bearings and other parts of. the compressor particularlywhen the compressor is recompressi'ng air from chamber 55 abov the oilin oil reservoir 40 back into the supply reservoir I at wh-ich time thepressure in the inlet pip I3 will be considerably above that of theatmosphere; 7

When the crank case I2 ischarged withair at a pressure exceeding that ofthe atmosphere as above mentioned this pressure will-tend to force oiltrom the crank caseout along the crank shaft and through thepressure-seal II. This sealwill efficiently prevent such loss of oilfrom the crank case only against, a certain degree of pressure thereinand another reason for using thereducing valve device 83 is therefore toprevent obtaining. a pressure in the. crank case-above said certaind'eg'ree so a's to' ensure that the seal II will function efiiciently.

The reducing valve'device 83 isof particular importane'c'when thecompressor is of. the compoundtype shown, in order to. cause boththehigh and'lcw pressure pistons 4 and 3 to operate as intended and to"avoid excessive loading of the low pressure piston, as will now bedescribed.

Let it be assumed thatQiii eifecting a hoisting operation the pressure'of. the air in reservoir I becomes eqnalise'd with thatinchamber 55inthec'il'reservo'ir 4'9; at for instance one hundred and fifteen pounds.If the reducing valve device 83 were not employed, then when the handle42 were returned to its vertical position shown this one hundred andfifteen pound pressure inchamber 55 would become effective at .theintake to the compressor 2 and thus at the pressure 'side of the lowpressure piston 3 upon its intake stroke. The low pressure piston 3 onits compression stroke would then increase the pressure of the,

air above the piston to a degree-above that in the supply reservoir Iand this air would therefore merely be forced through the inlet andoutlet valves for the high pressure piston 4 directly to said reservoir.The low pressure pistonj 3 would therefore operate under extreme loadand the high pressure piston 4 would: merely idle. Furthermore, in orderto take care of the large quantity of air displaced by the low pressurepiston 3 under such a condition excessively large inlet and outletvalves would be required to avoid loading of said piston by a pressurefar exceeding that in the reservoir I.

To avoid these difllculties, the reducing valve device 83 thereforefunctions to reduce the pressure of the air supplied from the chamber 55to the inlet of the compressor during recompression to a degree suchthat when theair. is discharged from the low pressure cylinder itspressure will be lower than in the reservoir I so: as to thus It hasbeenfound that by using the reducing valve device 83 and obtaining all thebenefits thereof, that recompression of the air from chamber 55 backinto the storage reservoir l is obtained in substantially the same timeas without the reducing valve device. It has also beenfound that byrecompressing the air from chamber 55, which may be under a relativelyhigh degree of pressure, back into the storage reservoir I the pressurein said reservoir may be completely restored in only about twentypercent of the time required for a corresponding restoration with theintake of the compressor open to the atmosphere Furthermore, restorationof the pressure in supply reservoir I by recompressing the air fromchamber 55 provides asaving in power consumed as great as for instanceforty percent, as -com pared to effecting such restoration by drawingair directly from the atmosphere at the inlet of the compressor. a I

The reducing valve device 83 will operate as above described to limitthe pressure in chamber 82 and thus at the compressor intake as long asthe pressure in chamber-55 ofthe oil reservoir is of a higher degreethan in chambers 82 and 92. However, when the pressure in chamber55-becomes reduced to a degreesubstantially equal to that in chambers 82and 92, the spring 96 will defleet the diaphragm 94 upwardly and movethe valve 89 to its fully open position shown.

With the valve 89 in its fully open position the compressor willcontinue to operate to recompress'the air from the oil reservoir chamber55 back into the air supply reservoir I until the pressure in saidchamber acting on diaphragm 35 of the governor cutout device 21 isoverbalanced by the opposing pressure of spring 39. This overbalancingwill be obtained when the pressure of the air in the oil reservoirchamber 55 and intake pipe I3 becomes reduced to some low degree such astwo pounds and when such occurs thespring 3,9 will return the diaphragm35 to its normal position shown 'tothereby close the valve 21 andopen'the valve 24 and thus cut the electric governor 20 into control bythe pressure of the air in 'the supply reservoir I. I

If at tnjjm the pressure in the reservoir I is at or abovethe cut-outadjustment .of the electric governor 20 said governor will immediatelyoperate to stop thejcompressori! in which case the relatively low degreeof air pressure still ex'- isting inchamber 5 5 above the oil inreservoir 40 will be bottled'up. However in case the pressure in thereservoir! isnot yet restored to the cutout adjustment of theelectricgovernor20 the compressor will continue to operate to compress air intothe tank I until such cutout pressure is ob.- tained at which time thegovernor will operate to stop the compressor. I

If the compressor 2 continues to operate after the cutout'cleviceZIoperatestO connect the electric governor 29 up for control by. thepressure of the'airin the reservoir I, this continuedoperation will"cause a further reduction of pressure in chamber 55 above the oil inreservoir 40, and this further reduction may reduce thepressure in saidchamber to substantially atmospheric pressure. Infcase the reservoir Iis not completely recharged at "the time the pressure ,in

chamber 55 thus becomes reduced to atmospheric pressure the compressor2Iwi1l continue to operate and draw air fromf the atmosphere: throughtheair strainer BIJfand past the check valve 85. It will thusbeapparentthat at-the time the compressor 2 stops operating the pressurein chamber 55 above the oillin reservoirv 4!] may be ofany degree fromsubstantially atmospheric pressure unto that existing at, the time thecutout device 2I operates to connect the governor 20 up for control fromthe reservoir I.

,When the hoist is iin its lowered or normal po- I sition it is intendedthat the reservoir I willjbe substantially filled with-oil as shown inthe drawing. Underthis condition a relatively small amount of compressedair from'the tank I'will be required to-displace the required amount ofoil from the reservoir, for raising the hoistto its elevated position. 1I v If a less amount of oil isin-the reservoir I, as may bethe casedueto loss by leakage after long use, a greater amount of compressed airwill be required fromthe airsupply reservoir I to displacetherequired.amount of oil from'the oil reservoir-to effect adesiredhoisting operation.-

Thus the amount of compressed air required from-the reservoir 'I toeffect a hoisting operation will varyaccording. tov the amount of oil inthe reservoir- I; Where the amount of air required for effecting ahoisting operation is of a minimum and is draw-nfrom the air supplyreservoir when charged to the'cutting-out point of the governor 20,reservoir I- may not"become-reduced to the cutting-inpoint' ofthegovernor 20. In such a case the compressor 2' will not be caused tooperate during the hoisting" operation; but upon movement of the lever42 back to its normal position will operate to merely recompress theairfrom'chamber 55 back into the air supply reservoir I andthereby' restorethe pressure in said reservoir to substantiallyits originalvalue. v

Where, however, the amount of compressed air needed for effecting ahoisting operation causes a reduction in pressure in reservoir I tobelow the cutting-in adjustment of the governor or in case the pressurein reservoir 1 is of such a reduced degree as to cause the governor tocut-in, even in case of .a completelyfilled oil reservoir, thecompressor 2 .may be caused to .operate as above described to completelyrecharge the air supply reservoir lduring a hoisting operfifteen poundsabove the cutout adjustment of the electric governor 20. However, exceptunder some extreme condition, such as in case of a small supply of .oilin the oil reservoir and the pressure obtained in :the air supplyreservoir 1 by recompression from chamber 55 may never attain the valuerequired to operate the safety valve device llll.

When the operator desires to lower the hoist 'heturns the handle 42 in aclockwise direction to a loweringposition at the right hand side of thenormal'position in which the handle is shown in the drawing. Thisoperation of the handle to the lowering position actuates the lever andthereby the plunger 49 to unseat the check valve 46 against the opposingpressure of the bias spring 41. With the air pressure in chamber abovethe oil in reservoir 40 reduced to or near that of the atmosphere theweight of the elevated body will then cause flow of liquid back throughthe supply pipe 45 and past the unseated check valve 46 into thereservoir 40 and this flow will continue until the body has beenreturned from its elevated position to its normal lowered position atwhich time the handle 42 may, if desired, be returned from its loweringposition to its normal position shown. The return of handle 42 to itsnormal position at this time is, however, of no consequence.

In case the handle 42 should be moved directly from its raising positionto its lowering position, as might possibly be done under certainconditions, the oil from the hoist will flow back through the supplypipe 45 to the reservoir 40 only as the pressure of the compressed airin chamber '55 is reduced by operation of the compressor to recompresssame back into the airsup- .ply reservoir I.. This recompression howeveroccurs rapidly so as to quickly evacuate the chamber 55 of compressedair and thus will not materially retard the lowering of the elevatedbody.

As above mentioned, a certain low degree of air pressure may be bottled.inchamber 55 above the oil in reservoir 40 at the time the cornpressorstops, this bottled pressure being determined by the pressure oLspring30 in the governor cutout device 21. The pressure of this spring needonly be suflicient to insure that the valve 24 will be open when thepressure in the compressor intake pipe I 3 is substantially that of theatmosphere, and may therefore be such as to require only a relativelylow pressure such as two pounds in the intake pipe for seating the valve24. The bottled pressure in chamber 55 under the condition abovementioned may,

therefore,betwopounds .and this is permissible since normally a greaterpressureis required to counteract the weight-of the. parts of hoistingmechanism connected to the oil supply pipe 45. Thus, even with a bottledpressure of two pounds in, chamber .55 above the oil in reservoir 40, acomplete lowering of the hoist is normally en- .sured.

Summary It will now be noted that the improved hoist control mechanismprovides for positive and selective raising and lowering operationsregardless of the load being elevated and ensures that the load or bodywill not be dropped during a raising operation or while the load is in araised condition, in case of failure of the compressed air in thesystem.

The system provides for most economical operation by recom'pressing theonce used compressed air from the oil reservoir back into the compressedair supply reservoir. It will be noted that the compressed air which hasbeen once used to effect a hoisting operation is never vented to theatmosphere unlessdue to some rare condition the recompression causessuch an increase in pressure in the supply reservoir as to cause openingof the safety valve device IN.

The reducing valve in the recompression connection to the intake of thecompressor insures intended compound operation of a compound Hcompressor, avoids excessive loading of and pos sible damage to any partof the compressor and also prevents loss of oil from the crankcase ofthe compressor when the crankcase is connected to the compressor inletand thus charged with compressed air.

The recompression system including the reducing valve device alsoprovides for obtaining a quicker recharge of the air supply reservoir.and a saving of power consumed by motor In to maintain said reservoir ina sufliciently recharged condition for operating the system, as comparedto a system not embodying the improved recompression feature.

It should also be noted that recompression of the air from chamber 55 inthe oil reservoir is insured regardless of the air pressure which may beacting in the supply reservoir I at the time the operating handle 42 ismoved out of its raising position, since the governor cutout device 2|will operate at this time to ensure operation of the compressor 2.

In case the recompression system fails for any reason with a load in anelevated position, the

relief valve I03 provides'for lowering of the load as described.

Having now described my invention, what I claim as new and desire tosecure by Letters Patent, is:

1. In combination, a first reservoir adapted to be charged withcompressed air, an air compressor having its inlet connected to an inletpipeand having its discharge opento said-reservoir and adapted toreceive air from said inlet pipe and to compress same intosaidreservoir, a governor device for controlling said compressor andnormally responsive'to the pressure of air in 'said reservoir andoperative upon -an increase in'such pressure to a desired degree'to stopsaid compressor and-upon a reduction in the pressure in said reservoirto a desired lower degree to start said-compressor, saidinlet pipehaving a communication with the atmosphere; a check valve insaidborhm'unication arranged toprovid'e for flow of air from theatmosphere to said'inlet pipe-and adapted to' be operated by pressureinsaid pipe to close s'aid communication, a second reservoiradapted tobe charged with compressed air at a pressure not exceeding that in saidfirst reservoir, valve means operative to open communication-betweensaid second reservoir and said 'inlet pipe to provide for flow ofcompressed air frorn 'said second reservoir' to the inlet 0f saidcompressor,-and means controlled bythe pressure in saidinlet pipe andoperative when the pressure therein'is increased to a chosen degreeabove that or the atmosphere to eiiect operation 'of said governordevice to cause said compressor to operateregardless of the pressure insaid first reservoir.

2. In-combination, a first reservoir adapted to becharged with"compressed air, *an air com-'- pressor adapted to':cha1'ge saidreservoir, an air inlet pipe forsaid -compressor a-dapted to be opened"to the atmosphere, a governor device for controlling the operation'ofsaid compressor and normally controlled by the pressure of air in saidreservoir and operative upoiran increase in such' pressure 'to a chosendegree to stop said cornpressor and upon a reduction insuch pressure toa 'chosen lower" degree to start said compressor, cutout meanscontrolling cornmunicaw tionbetween'said governor d evice and reservoirand normally establishing'such communication to render said governordevice responsive.to1the' pressure of fiuid in said reservoir andoperative to close such communication to thereby render said overnordevice: operative toefiect operation of sai d compressorregardless-g offthe pres sure in said reservoir, means 'eontrolled by the pressure of.fluid in said inlet jpipe',oi ;'cont1'ol-;

ling said cutout means and operative when the pressurein said inletpipeoi ad'egree sub stantially no greater than that of the atmosphere toactuate said cutout means to effect opening of said communication andwhen of a greater degree to actuate said cutout means 'to effect closingof said. communication, a'second reservoir adapted to be charged withfluid at a pressure not exceeding that in said first reservoir, a valveoperative to connect said second reservoir to said inlet pipe forsupplying compressed air from said second reservoir to the inlet of saidcompressor, and a check valve operative upon the supply of compressedair from said second reservoir to said inlet pipe to close communicationbetween said inlet pipe and atmosphere.

3. In combination, a first reservoir adapted to be charged withcompressed air, an air cornpressor adapted to compress air into saidreservoir, an air inlet pipe for said compressor, a compressor governorfor controlling said compressor normally responsive to the pressure ofair in said reservoir and operative to effect operation of saidcompressor when the pressure of the air in said reservoir is less than achosen degree and to stop operation of saidcompressor 'when the"pressure of air in saidmreservoir is increasedto" a chosen'higherdegreeya second reservoir adapted to be charged withcompressedair'atapressure not exceeding that in said first reservoinvalve means operative to connect" said second reservoir to said inlet pipe to supply-compressed air from said secondreservoir to the inlet ofsaid compressor, and means. operative by the 'pressur'e ofairsupplied'from said second reservoir tosaid inlet pipe to effectoperation of said governor to cause said compressor to operatereg'ardless of the pressure of fluid insaid first reservoir; said meansbeing operative when 'the pressure in said second reservoi'r'is reducedby operationof i said: compressor to a chosen low'degree to conn'ectsaid governor to said-first reservoir for control by the air pressurethereini I 1 z 4. A hydropneumatic hoist control mechanism comprisingaliquid reservoir containing a body; of liquid and having-above the"liquid an airchamber to which compressed air is adapted'to be suppliedfor displacing the liquid to-efiec't' a hoisting operation; a certain"minimum *pres sure of compressed 'air being required :in'sa'idchamber toinitiatesaid" hoisting-operation, 'a compressed'air: supply reservoir,an air compres-'- sor adapted to-compress air into-said'supply betweensaid compressed air'supply reservoir andsaid chamber and to connectfsaidchamber'to said inletpipe-for supplying-compressed air from said chamberto the inlet"of -said compressor,

a pressure governor normally responsive 'to the pressurein said air'supply reservoir 'ror imainf taining the pressure ithe'r'ei'n :be'tween'certainchosen limits, and means operative upon supply! of compressed airfrom: said "chamber to said" inlet pipe .to effect operation of saidgovernor to cause said compressor to operate to recompress the-air fromsaid chamber'into' said reservoir" regardless of the pressure of fluidirr saidreservoir.. r a 1.

5. 'A- hydropneumatic' hoist control mechanism;

comprising" a liquid 're'se'rv'oir containing a body of liquid andhaving above the liquid anair" chamber toxwhich 'com'pressed' air is'adapted to 'be'suppli'ed .for displacing the liquid to'effect a hoistingoperation, a -'certain-ininimum pressure of compressed" air beingrequired in said chamber.to initiate s'aid' hoisting operation, acompressed air supply reservoir, an air' compressor adapted to compressair into said supply reservoir, an air intake pipe for said compressor,manual means operative to open communication between said supplyreservoir and said chamber for supplying compressed air to act on saidliquid for effecting a hoisting operation, said manual means beingoperative to close communication between said compressed air supplyreservoir and said chamber and to connect said chamber to said inletpipe for supplying compressed air from said chamber to the inlet of saidcompressor, a governor for controlling said compressor and normallysubject through a passage to the pressure of compressed air in saidsupply reservoir and operative when such pressure exceeds a chosendegree to stop said compressor and when of a less degree to start saidcompressor, and means operative upon supply of compressed aircommunication between said passage and reservoir and to open saidpassage to the atmosphere so long as the pressure in said chamber isabove said minimum degree and to reconnect said passage to said supplyreservoir when the pressure in said chamber is less than said minimumdegree, to thereby render said compressor operative to compress thecompressed air from said chamber into said supply reservoir until thepressure in said chamber is reduced to said minimum pressure regardlessof the degree of pressure acting in said supply reservoir.

6. A hoist control system comprising a hydraulic reservoir containing abody of liquid and having above the liquid body a chamber adapted toreceive compressed air for displacing said liquid to effect a hoistingoperation, an air supply reservoir, an air compressor operative tocompress air into said reservoir, a governor controlled by the pressureof air in said reservoir for controlling the operation of saidcompressorzand providing for the maintenance of the air pressure in,said reservoir between chosen limits, manually operative valve meansmovable to a position for supplying air from said supply reservoir tosaid chamber to displace liquid therefrom and movable out of saidposition to close communication between said reservoir and chamber andto connect said chamber to the intake of said compressor, and meansoperative by the pressure of air supplied from said chamber to theintake of said compressor to effect operation of said compressor torecompress the air from said chamber back into said reservoir regardlessof the degree of pressure in said reservoir.

,7. A hydropneumatic hoist control system comprising a hydraulicreservoir containing a body of liquid adapted to be displaced bycompressed air supplied to a chamber above the liquid to effect ahoisting operation, a compressed air supply reservoir, an air compressorfor charging said air reservoir, a pressure governor arranged to becontrolled by the pressure of air in said air supply reservoir forcontrolling the operation of said compressor and operative to regulatesaid compressor to maintain the pressure in said air reservoir betweenchosen limits, and manually operable means having one position forventing compressed air from said chamber and movable to another positionfor connecting said chamber with said air supply reservoir to there-- byprovide compressed air on saidliquid to effect displacement thereof,saidv manually operable means comprising two valves, means connectingsaid valves for movement in unison, one of said valves constituting asupply valve controlling from said chamber to said inlet pipe to closecommunication between said air supply reservoirian'd said chamber andthe other valve constituting an'exhaust valve controlling communicationbetween said chamber and an opening for releasing compressed air fromsaid chamber, the said means-connecting said valves providing for theclosing of one valve upon opening of the other,'a movable abutmentconnected with said valves and constantly subject on one face to thepressure of the compressed air in'said supply reservoir and normallysubject on the opposite face to the pressure of air from said supplyreservoir, spring means acting on said valves for closing said supplyvalve and opening said exhaust valve when the opposite sides of saidmovable abutment are both subject to'the pressure of air from saidsupply reservoir, pilot valve means controlling communication betweensaid opposite side of said movable abutment and said supply reservoirand operative to close same and to vent the compressed air fromsaidopposite side of said abutment for thereby rendering said abutmentoperative to open said supply valve and close said exhaust valve, alever operative by manualpressure to effect operation of said pilotvalve means tovent compressed air from said QPDOsite side of saidabutment means, and means operative upon release of manual pressure onsaid lever to actuate said pilot valve means to reconnect said oppositeside of said abutment to said compressed air supply reservoir to therebyrender said spring means effective to close said supply valve and toopen said exhaust valve.

8. A hydropneumatic hoist control system comprising a hydraulicreservoir containinga body. of liquid adapted to be displaced bycompressed air supplied to a chamber above the liquid to effect thehoisting operation, an air supply reservoir, an air compressor operativeto charge said reservoir with compressed air, manually controlled valvemeans having one position for supplying compressed air from said airsupply reservoir to said chamber to effect displacement of liquid fromsaid hydraulic reservoir, and another position for closing communicationbetween said air supply reservoir and chamber and for connecting saidchamber to a pipe-connected said compressor to withdraw the compressedair from said chamber.

BURTON S. AIKMAN.

